Chemical-mechanical polishing (CMP) is performed in the processing of semiconductor wafers. A standard CMP apparatus has a circular polishing pad and a rotating carrier for holding a semiconductor wafer. An abrasive slurry is used on the polishing pad. After a CMP operation, residual particles are left on the surface of the semiconductor wafer. These residual particles need to be removed.
Semiconductor wafers are typically cleaned in a cleaning apparatus which includes one or more brush stations each having a pair of rotary brushes for cleaning the major surfaces of the wafers. A conventional cleaning apparatus 10 is illustrated in FIG. 1. The cleaning apparatus 10 includes a pair of brushes 11 that clean the major surfaces of a semiconductor wafer 14 placed therebetween. The semiconductor wafer 14 is supported by rollers 16, which are also used to rotate the wafer. The cleaning apparatus 10 includes at least one spray bar 18 to direct a spray of fluid towards the semiconductor wafer 14.
As semiconductor processes continue to achieve smaller line widths to create semiconductor wafers with greater capacity, post CMP defects control becomes more important for improving wafer yield and reliability. A key factor in brush cleaning is to precisely control the distance between the brush and the semiconductor wafer. If the separation distance is too tight, the residual particles from the CMP operation will scratch 20 the semiconductor wafer 14 as they are brushed off, as illustrated in a highlighted section 21 of the wafer as provided in FIG. 2. If the separation distance is to loose, some of the residual particles will not be removed. For example, a residual particle 22 may cause a short between two lines 24 and 26, as illustrated in a highlighted section 27 of the wafer as also provided in FIG. 2.
After the cleaning apparatus, the semiconductor wafer is placed in a drying apparatus. A conventional drying apparatus is also referred to as a spin-rinse/dryer, and includes a processing chamber comprising a rinsing section and a drying section adjacent thereto. The sequence in the drying apparatus includes spinning the semiconductor wafer in the rinsing section while rinsing with a rinsing liquid, and then spinning the wafer in the drying section to dry. The rinsing section is to remove any residual particles not removed by the cleaning apparatus, whereas the drying section is to remove any residue marks left on a semiconductor wafer after rinsing.
Vapor within the drying section needs to be contained and exhausted so as to avoid contamination of the semiconductor wafer as it is removed from the drying apparatus. As the semiconductor wafer is removed, DI water or an IPA flow rate spike may cause a water mark or IPA to condense on the semiconductor wafer. This will lead to wafer yield and reliability being decreased. One approach to avoiding contamination is disclosed in U.S. Pat. No. 7,513,062. An exhaust control cap is provided for the drying apparatus and includes an exhaust manifold and a nitrogen blanket manifold. A gas flow module is coupled to the exhaust manifold and the nitrogen blanket manifold to control the vapor flow rate, the exhaust rate and the nitrogen blanket flow rate. In addition, an exhaust line may maintain a vertical laminar flow through the output portion, as well as diluting any vapor that may escape from the drying section.
Further developments to contain and exhaust vapor from the drying section of a drying apparatus are still desired. This is particularly so if the rinsing liquid within the rinsing section is toxic.